Unquenching the Schwinger Model (revised)

We study the quenched and unquenched lattice Schwinger model with Wilson fermions. The lowest non-trivial order of the systematic expansion recently proposed by Sexton and Weingarten is shown to allow good estimates of long distance physics from quenched configurations. Results for the static potential and the lowest bound state mass are presented.Comment: 4 pages, 2 figures, self-unpacking uuencoded compressed postscript Contribution to Lattice 95 [Revision: value corrected on p.3

The Numerical Estimation of the Error Induced by the Valence Approximation

We describe a systematic expansion for full QCD. The leading term in the expansion gives the valence approximation. The expansion reproduces full QCD if an infinite number of higher terms are included.Comment: 3 pages, latex, no figures, requires espcrc2.sty (included at end) Contribution to Lattice 94 proceeding

Approximate actions for dynamical fermions

Recent developments and applications of approximate actions for full lattice QCD are described. We present first results based on the stochastic estimation of the fermion determinant on $12^3\times 24$ configurations at $\beta=5.2$.Comment: 3 pages, Latex, no figures, Contribution to Lattice 97, The XV International Symposium on Lattice Field Theory, Edinburgh 22-26 July 199

Multiple molecular dynamics time-scales in Hybrid Monte Carlo fermion simulations

A scheme for separating the high- and low-frequency molecular dynamics modes in Hybrid Monte Carlo (HMC) simulations of gauge theories with dynamical fermions is presented. The algorithm is tested in the Schwinger model with Wilson fermions.Comment: Lattice2002(algor), Talk presented at Lattice 2002, MIT. 3 pages, 2 figure

Wind Turbine Design, Performance, And Economic Analysis

This paper is an investigation of the economic feasibility of small scale (1 to 70 kw) wind energy conversion systems (WECS). It can be shown that the wind system productivity and therefore the relative cost of the product which it produces is completely dependent on the wind regime under consideration. The mean wind speed, standard deviation, and wind profile are the most significant parameters to be used in the investigation of cost of product from a wind system. The purpose of this work is not to find an optimum wind system, but to give the reader enough information to make an informed decision as to whether or not a wind system configuration could meet the particular need under consideration; the wind system appropriate to a residential home owner is quite different from that for a dairy farmer, for example. The decision ultimately boils down to the cost of usable energy, i.e., cents/kwhr of those kwhrs thatcan be used. Various wind machines will be designed and priced. They will then be superimposed onto different wind regimes modeled by the Weibull distribution for a first approximation of the cost of product at that site using that machine. It will be clear that the same machine will have different cost effectiveness at different sites, and that the cost-ofuseful-energy-product will vary, site-to-site, for the same machine

Modeling real gases and liquids using a modified van der Waals equation of state.

Equations of state attempt to describe the relationship between temperature (T), pressure (P), and molar volume (v) for a given substance or mixture of substances. The ideal gas law is the simplest form of an equation of state. An ideal gas can be considered as a large quantity of small molecules that have no friction, no attractive or repulsive forces. The ideal gas law is a reasonable approximation at low pressures and high temperatures, but not at higher pressures and lower temperatures. Thus, better methods for predicting real gas behavior have been continuously introduced over the past 200 years. Another approximation is to assume that gas atomes and molecules behave as hard spheres. These spheres are incompressible and only repulsive forces are significant at the moment of collision. A recent modification made to the van der Waals equation of state (VDW) incorporates the hard sphere model, giving better representation of the van der Waals parameters over a broader temperature and pressure range. The efficacy of this modified van der Waals equation of state was assessed for six previously researched compounds -ethane, propane, n-butane, n-pentane, argon and water. Physical property charts (specifically molar volume and molar enthalpy charts) were developed for these substances using the original VDW and modified VDW, as well as the Redlich-Kwong (RK) and Redlich-Kwong-Soave (RKS) equations of state. Results for molar volume revealed that for the four hydrocarbons, the modified VDW compared best with the given experimental data, but not for argon and water. Results for molar enthalpy showed the original VDW compared more favorably with experimental data that the original VDW, but not as well as the RK equation of state

Numerical Stability of Lanczos Methods

The Lanczos algorithm for matrix tridiagonalisation suffers from strong numerical instability in finite precision arithmetic when applied to evaluate matrix eigenvalues. The mechanism by which this instability arises is well documented in the literature. A recent application of the Lanczos algorithm proposed by Bai, Fahey and Golub allows quadrature evaluation of inner products of the form $\psi^\dagger g(A) \psi$. We show that this quadrature evaluation is numerically stable and explain how the numerical errors which are such a fundamental element of the finite precision Lanczos tridiagonalisation procedure are automatically and exactly compensated in the Bai, Fahey and Golub algorithm. In the process, we shed new light on the mechanism by which roundoff error corrupts the Lanczos procedureComment: 3 pages, Lattice 99 contributio

Systems Integration Processes for NASA Ares I Crew Launch Vehicle

NASA's Exploration Initiative will require development of many new elements to constitute a robust system of systems. New launch vehicles are needed to place cargo and crew in stable Low Earth Orbit (LEO). This paper examines the systems integration processes NASA is utilizing to ensure integration and control of propulsion and nonpropulsion elements within NASA's Crew Launch Vehicle (CLV), now known as the Ares I. The objective of the Ares I is to provide the transportation capabilities to meet the Constellation Program requirements for delivering a Crew Exploration Vehicle (CEV) or other payload to LEO in support of the lunar and Mars missions. The Ares I must successfully provide this capability within cost and schedule, and with an acceptable risk approach. This paper will describe the systems engineering management processes that will be applied to assure Ares I Project success through complete and efficient technical integration. Discussion of technical review and management processes for requirements development and verification, integrated design and analysis, integrated simulation and testing, and the integration of reliability, maintainability and supportability (RMS) into the design will also be included. The Ares I Project is logically divided into elements by the major hardware groupings, and associated management, system engineering, and integration functions. The processes to be described herein are designed to integrate within these Ares I elements and among the other Constellation projects. Also discussed is launch vehicle stack integration (Ares I to CEV, and Ground and Flight Operations integration) throughout the life cycle, including integrated vehicle performance through orbital insertion, recovery of the first stage, and reentry of the upper stage. The processes for decomposing requirements to the elements and ensuring that requirements have been correctly validated, decomposed, and allocated, and that the verification requirements are properly defined to ensure that the system design meets requirements, will be discussed